Recently I read some reprints of old Lee-Kirby Fantastic Four comics. In them a recurring event is the foiling of some nefarious Doctor Doom plot, which then sees Ben Grimm suggesting that they throw the Doctor into jail. "No Ben," Reed Richards then says, "Doom is the head of state of Latveria, and as such is entitled to diplomatic immunity". This always seemed a bit unlikely, but it was a handy way of ensuring that Doom was able to return in a month's time to threaten American freedom once more.
Bizarrely, it turns out that Reed Richards was acting correctly here, as heads of state (and other senior state officials) are in fact entitled to full immunity when fulfilling the functions of their office, which in Doom's case would include trying to take over the world.
This is the kind of important matter my course in International Relations covers.